b'AEGC 2023Short abstractsstreamer surveys. In most cases where acquisition differencesGranites of different periods and intrusion process were widely are minimal, standard 4D processing techniques are sufficient.distributed and underlined the sediments accompanied by However, cases in which there is lack of good repeatability oftensome deep faults. As for the HDR delineation, 3D models results in strong 4D noise which require more sophisticatedshowed a potential area along Gonghe town and Dongba. approaches and technology. The density and susceptibility were estimated at over 2.6 g/cm3 and 4103 SI separately, when referred with exiting HDR In our case study in the Northern Carnarvon Basin,distribution along the geological profile of DR4QR1DR3DR2 environmental factors introduced some differences betweenwells. The upper boundary of HDR was outlined at the depth the planned and acquired 4D monitor survey. Thus, aof around 2000 m, and the volume of HDR was then estimated deterministic 4D de-striping correction processing flow,around 6100 km3 above 3500 m depth. The appearance of instead of conventional survey matching, was deployed tothe density and susceptibility models was affected by the suppress acquisition-related 4D noise as a result of waterlithology, stress and hydrothermal alteration. More precise velocity and tidal height changes. This flow decoupled eachgeophysical methods including the microgravity, seismic and noise-contributing factor based on its physical characteristics.MT (magnetotelluric) surveys would be more applicable at the In addition, the strong currents that led to source positioningHDR exploitation stage.errors and streamer feathering, significantly degraded the 4D signal-to-noise ratio. To better reveal true 4D signals, least-squares migration (LSM) was adopted to reduce migrationImaging complex geology using 3D seismic: Unique artifacts and better compensate for illumination variation. 4Ddepth imaging workflows applied to the Carosue Dam noise was greatly reduced in the LSM process by mitigatinggold deposit, Western Australia.position errors via demigration and remigration techniques.With a comprehensive 4D processing flow, we were able toSasha Ziramov 1 Jai Kinkela1, Carl Young2 and Greg Turner1achieve a reduction of NRMS from 0.7 to 0.1. This resulted in a better 4D signal for interpretation of reservoir performance and1 Hiseisactivity, in our case, much improved visibility of the subsidence. 2 Northern Star Resources Limited Hard rock seismic processing experiences a unique set of Interpretation of gravity and magnetic data on thechallenges relative to sedimentary environments. They often consist of complex geological settings comprising steeply hot dry rocks (HDR) delineation for the enhanceddipping interfaces and heterogeneities (stratigraphy, faults, geothermal system (EGS) in Gonghe town, China. fracture and shear zones etc.), low intrinsic signal to noise ratio Tom Zhao , Zhaofa Zeng and complex near surface conditions (strongly contrasting 1 2weathered overburden relative to bedrock). These complexities 1 University of New South Walesrequire sophisticated imaging approaches to accurately 2 Jilin University reposition the seismic energy back to its true spatial location. In this study we demonstrate how the latest generation of seismic As a new kind of renewable and environmental-friendlyimaging algorithms (migration) that have been successful in energy to generate electricity, hot dry rocks (HDR) geothermalthe oil and gas environment can be adapted to overcome the reservoirs have been studied, along with the enhancedunique challenges often encountered in mineralised terrains. geothermal system (EGS). Geophysical methods have beenSpecifically, we explore pre-stack depth imaging techniques used for the geological characterisation in different scales.such as Reverse Time Migration (RTM) and how coupled with a The small-scale geophysical data are required for the localunique approach to velocity model building we can achieve a geological analysis so as to provide prior information forsignificant uplift in the imaging quality relative to time imaging HDR modelling. Gonghe basin is in the northeast margin ofapproaches.the QinghaiTibet Plateau. Several drilling records indicate that this basin is a potential HDR prospecting area with highThis specific case study looks at a high resolution 3D (three geothermal gradient, high heat flow and widespread igneousdimensional) reflection survey acquired over the Carosue Dam rock distribution, especially the Gonghe town (Qiabuqia) alonggold operation in Western Australia. The primary objective was with its neighbouring area. Gravity and magnetic surveys wereto image steeply dipping shears known to host gold with a carried out here. To better understand the areal and verticalfocus on economic depths of investigation down to 2 km. In this distribution of the HDR, the gravity and magnetic data werestudy we are able to demonstrate how the reprocessed seismic inverted using 2D manual inversion and 3D cross-gradientdata shows a remarkable level of correlation with known shear joint inversion based on the smooth l0l0 norm constraint ofzones logged from drilling all the way up to the top of fresh minimum support functional stabiliser. The 2D model showedrock as well as highlight other seismic features that provide the sedimentary cap with a thickness of around 10001500 m.compelling targets that warrant further investigation.FEBRUARY 2023 PREVIEW 156'